Method of making concrete pipes

ABSTRACT

The specification discloses a method and apparatus for manufacturing concrete pipes by depositing a layer of green concrete (i.e., concrete which has not set) on a mandrel, winding helically around the deposited green concrete a flexible, binding member to consolidate and retain the concrete on the mandrel, and winding helically a flexible reinforcing member under tension around the concrete before the concrete has set.

' United States Patent Luckett et al.

[ 51 Dec. 23, 1975 METHOD OF MAKING CONCRETE PIPES Inventors: Peter Robert Luckett; Jack Sidney Mobbs, both of Ashford; Alan James Harris, London, all of England Assignee: Stelmo Limited, Ashford, England Filed: May 18, 1973 Appl. No.: 361,686

Foreign Application Priority Data May 19, 1972 United Kingdom 23600/72 US. Cl. 156/171; 29/452; 138/175; 138/176; 156/172; 156/173; 156/187;

Int. Cl. ..B28B 21/48; B28B 21/64; B65H 81/00 Field of Search 156/172, 173, 188, 192, 156/195, 392, 429, 430, 431,171,187,191; 138/175, 176', 425/111; 264/228; 29/452 References Cited UNITED STATES PATENTS 12/1954 Vessels .1 264/228 3,243,949 4/1966 Cilker et al. 156/172 3,489,626 1/1970 Rubenstein 156/171 3,506,752 4/1970 Varnell et a1. 29/452 3,520,749 7/1970 Rubenstein 156/173 3,630,237 12/1971 Vamell 138/176 3,706,615 12/1972 Nishiyama et a1. 156/192 3,711,935 1/1973 Hiraga 29/452 3,740,291 6/1973 Mallard 156/392 3,761,557 9/1973 Werner 138/176 Primary ExaminerDouglas J. Drummond Assistant ExaminerBasil J. Lewris Attorney, Agent, or FirmBrowne, Beveridge, DeGrandi & Kline 57 ABSTRACT The specification discloses a method and apparatus for manufacturing concrete pipes by depositing a layer of green concrete (i.e., concrete which has not set) on a mandrel, winding helically around the deposited green concrete a flexible, binding member to consolidate and retain the concrete on the mandrel, and winding helically a flexible reinforcing member under tension around the concrete before the concrete has 15 Claims, 3 Drawing Figures US. Patent Dec. 23, 1975 METHOD OF MAKING CONCRETE PIPES BACKGROUND OF THE INVENTION The invention relates to methods of manufacturing concrete pipes, and to apparatus for manufacturing concrete pipes.

Concrete pipes for carrying fluids under pressure require a circumferential reinforcing high tensile steel wire which is pre-tensioned to ensure that the concrete is always in compression.

One known method of making such pipes is to cast the pipe with high tensile wire embedded therein on a core and then to inflate the core to expand the concrete and wire thereby tensioning the wire and maintaining the core inflated until the concrete has set. A disadvantage of this method lies in the very expensive specialized moulding equipment required.

Another known method is to cast a conventional pipe which after it has set is of sufficient thickness and strength to withstand the circumferential pressure of the tensioned wire applied to it. The wire is prevented from corrosion by the application of a further layer of concrete.

The object of the invention is to provide an improved method and apparatus for making concrete pipes having a tensioned flexible reinforcing member which exerts a circumferential pressure on the concrete without the need of expansion moulding equipment as described above.

SUMMARY OF THE INVENTION The invention provides a method of manufacturing concrete pipes comprising depositing a layer of green concrete (i.e., concrete which has not set) on a mandrel, winding helically around the deposited green concrete a flexible binding member to consolidate and retain the concrete on the mandrel, and winding helically a flexible reinforcing member under tension around the concrete before the concrete has set.

The flexible binding member may be wound on to the green concrete simultaneously with the flexible reinforcing member, the reinforcing member being wound on to a part of the concrete which has already been wound with the binding member.

A further layer of green concrete may be deposited on the concrete deposited on the mandrel after binding and reinforcing and before that concrete has set.

The invention further provides apparatus for making concrete pipes, comprising a mounting for a mandrel rotatable about a substantially vertical axis, a hopper for concrete movable relative to the mounting along said axis and having a hole through which a mounted mandrel may project, means for supplying a flexible binding member for winding around concrete deposited on the mounted mandrel below the hopper, and means for supplying a flexible reinforcing member for winding around concrete deposited on the mounted mandrel including means for tensioning the reinforcing member as it is wound around deposited concrete.

The applicants have discovered that by winding a binding member around the green concrete core, it is possible to wind the wire member around the core under tension without the core member cutting into the core which then tends to slump or spall off. It seems that the binding member set up forces in the green concrete that resist the cutting action and the final articles'have showed no tendency to slump or spall during curing.

A method'according to the invention has the advantage over the last described prior art methods that the wire is wound under tension onto the green concrete while it is still on the mandrel so that the amount of concrete can be'reduced since it is supported circumferentially by the mandrel which carries the binding moments induced by the winding load. Furthermore the number of operations is reduced since the core concrete does not need to be left to harden before applying the tensioning member. The quality of the finished product is also improved since the method permits an outer concrete coat to be applied to encapsulate the Wire member while the core concrete is still green so that the two concrete layers set and cure together to form a homogeneous concrete pipe.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic perspective view of the apparatus;

FIG. 2 is a cross-sectional view of part of two connected pipes made in accordance with the invention; and

FIG. 3 is a detailed view of part of the mandrel.

DESCRIPTION Referring to FIG. I, the apparatus comprises a base 10, having four upstanding columns 1 I, the upper ends of which are connected together by a rectangular frame 12. A platform 13 is slidably mounted on the columns 11, and has a circular hole 14 formed in the middle thereof.

Four chains 15 are connected, one adjacent each column 11 respectively, to the platform 13, and pass over pulleys 16 rotatably mounted on the frame 12. Four idler pulleys 17 are rotatably mounted on the frame part-way between two columns 1 l, and the cylinder 18 of a double'acting hydraulic ram is secured to the frame adjacent the roller 17. The four chains 15 pass over the roller 17 and are connected together and to a wire cable 20 bymeans of a coupling 21, the wire cable 20 passing around a pulley 22 provided on the end of the piston rod 23 of the hydraulic ram and the end of the wire cable 20 being anchored to the frame 12. Expansion and contraction of the ram 19 respectively raises and lowers the platform 13 relative to the base 10.

The base 10 is provided with a mounting for a mandrel, which mounting comprises a shaft 25 rotatably supported in the base, the shaft having a flange (not shown) on the upper end thereof. Part-way between the flange and the base a sprocket 26 is attached to the shaft 25. A mandrel, such as that shown at 27, is bolted to the flange so that it is supported by and rotates with the flange and shaft 25.

A hopper 29, of generally part-conical shape, rests within the hole 14 provided in the platform, the smaller diameter end of the hopper fitting with a predetermined small clearance around the mandrel 27. Attached to the outer surface of the hopper 29,- below the platfon'n 13, are four electrically powered vibrators 30.

A roll 31 of polypropylene string for winding around a partly manufactured pipe is rotatably mounted beneath the platform 13. String from the roll 31 passes through a tensioning device comprises a pair of plates 32, one of which is secured to a rod 33 attached to the platform 13. The other plate has a hole through which the rod 33 passes, a helical spring around the rod urging the other plate towards the one plate, there being a nut (not shown) being threaded on the rod 33 to adjust the tension in the spring. From the tensioner, the string passes through a tubular guide 34 to guide the string for winding around the mandrel.

Means for supplying a high tension steel reinforcing wire under tension for winding around the mandrel are provided, and comprise a roll 35 of steel wire mounted on a pair of brackets 36 attached to the ground. Attached to a frame (not shown) is a vertically extending shaft 37 on which are rotatably mounted three pulleys 38, and spaced from the shaft 36 is a further vertically extending shaft 39 mounted for rotation in the frame. Three pulleys 40 are rigidly attached to the further shaft, which also has two sprockets 41 and 42 rigidly attached thereto. A motor 43 is arranged to drive a gearbox 44 the output shaft 45 of the gearbox carrying a sprocket 46, and an endless chain 47 is passed around the sprockets 46 and 41.

A hydraulic ram 48 is fastened to the platform 13, the piston rod 50 of the ram carrying a pulley 49 on the free end thereof, and the free end of the cylinder having two pulleys 51 and 52 rotatably mounted thereon. A tubular guide (not shown) is provided between the pulley 52 and the mandrel 27 on the lower side of the platform 13, and a further tubular guide 53 is provided between the uppermost pulley 40 and the pulley 51.

Wire from the roll 35 passes around the lowermost pulley 38, then the lowermost pulley 40, the intermediate pulley 38, intermediate pulley 40, uppermost pulley 38 and the uppermost pulley 40, from which the wire passes through the guide 53 and around the pulley 51 mounted on the cylinder of the ram 48, around the pulley 49 on the piston rod 50, then around the pulley 52 on the cylinder and through the guide tube to the mandrel.

The hydraulic ram 48 is connected to a source of constant pressure hydraulic fluid. An endless chain connects together the sprockets 42 and 26, the number of teeth in the sprockets being such that the peripheral speed of the pulleys 40 is less than the peripheral speed of the mandrel 27.

A second, similar steel reinforcing wire supplying means (not shown) is provided on the opposite side of the apparatus to that means shown, and has been omitted from the drawing for the sake of clarity. In addition, the hydraulic ram 48 in each case is provided with three pulleys on the piston rod thereof and four on the cylinder thereof (as opposed to the one and two pulleys respectively shown), so that there are six falls of wire passing around the pulleys. In the diagrammatic view of FIG. 1, only two falls have been shown for clarity.

FIG. 3 shows a detailed view of an end portion of the mandrel 27. Two end plates 60, each having a peripheral groove 61 and axial holes intersecting the groove 6], are located one adjacent each end of the hollow mandrel, and longitudinally extending reinforcing wires passed through the axial holes, so that the wires are spaced from the outer surface of the mandrel. On each end of each wire clamps 63 are fastened, and one of the end plates is then pulled axially away from the end of the mandrel to tension the longitudinal wires until a spacer 64 can be inserted between the respective end of the mandrel and the plate 60. The thickness of the spacer is such that when inserted as shown, the longitudinal wires have the required tension.

In place of the clamps 63 the end of each wire may be buttoned," deformed to provide an integral head which engages the plate 60.

To use the apparatus described above together with a mandrel prepared as just-described, the mandrel is bolted to the flange on the shaft 25 and the platform 13 moved to its lowermost position. The reinforcing wire from each of the two rolls is routed as described above. and each free end anchored to the lower plate 60 of the positioned mandrel String from the roll 31 is anchored to the mandrel just above the anchoring of the wire.

Green concrete (i.e., concrete which has not set) is poured into the hopper 29 and the vibrators 30 switched on. The motor 43 is also switched on, and hydraulic fluid at a predetermined constant pressure is supplied to the ram 48. The ram 18, 23 is actuated to move the platform slowly upwardly.

The clearance between the base of the hopper 29 is such that a layer of concrete is deposited on the mandrel as the platform 13 is gradually raised, the longitudinal reinforcing wires on the mandrel being embedded in a layer of concrete. Rotation of the mandrel winds helically a layer of string on to the deposited green concrete immediately below the hopper 29, and simultaneously winds both reinforcing wires on to the concrete on a part which has already been wound with string. The string serves to consolidate the concrete deposited, and to retain the concrete in position as the reinforcing wire is wound on. The two wires are wound on in the manner of a two-start thread, the wires becoming partially embedded in the concrete. Rotation of the mandrel also assists depositing of the concrete in a uniform layer. Concrete is added to the hopper 29 as necessary during movement of the platform 13.

The wire is tensioned by means of the differential speed between the peripheries of the pulleys 40 and the concrete deposited in the mandrel, the tension being maintained constant by the hydraulic rams 48. In practice, the wire is wound on such that the tension stresses the wire to about of the ultimate stress, some of which stress relaxes leaving a portion of this stress remaining in the wire after the pipe is completed.

When concrete has been deposited on the whole of the length of the mandrel and the string and wire wound on over that length, the string and both wires are anchored to the upper plate 60, and then cut through. The vibrators are turned off, and the platform is immediately returned to its lowermost position. The platform is then raised again slowly, concrete being added to the hopper 29 as necessary, to deposit a further layer of green concrete on the green concrete already deposited after winding with string and wire, before that concrete has set. String may be wound around the second layer deposited on the first layer in a similar manner to the string wound on to the first layer of concrete. The two layers thus consolidate together to form a homogeneous wall for the pipe.

An alternative method of using the apparatus is not to wind the wire on to the concrete immediately after winding on the string. When the whole of the mandrel has had a layer of concrete deposited thereon and the string has been wound around the deposited concrete, the platform 13 may be slowly lowered, the wire being wound on during the lowering of the platform. When the platform is at its lowermost position, the wire may be terminated, and the platform raised again to deposit the second layer of concrete on the layer already deposited and bound with string.

Materials other than the polypropylene string may be employed for binding around the first layer of depos-- ited concrete; for example a woven or textile or metallic tape may be employedThe string, or tape if used, may be wound on simultaneously from two or more rolls to cover a greater area of the layerof concrete, if required. A convenient way of terminating the reinforcing wires is to reduce the pitch of the helix for the two last turns, whilst reducing the tension in the wire, a clip then being used to clamp the free end to the preceding turn. The friction of the wire against the concrete in the two last turns serves to hold the tension in the other turns of the wire.

After completion of the pipe, the mandrel is removed from the apparatus and placed aside while the concrete sets. When set, the ends of the longitudinally extending reinforcing wires are cut through the slot 61, and then the wound wires cut from the anchorings to the plates 60. The plates are removed from the pipe, and the mandrel then removed. To assist removal, the mandrel may be collapsible, or may have a sector removable therefrom subsequently allowing a small reduction in the diameter of the greater part of the mandrel. Alternatively, the mandrel may be hollow and may remain in place within the concrete wall to form a lining for the pipe. The short projecting ends of the longitudinally extending wires may be ground flush with the end of the concrete after removal of the plates 60.

In order to allow axial joining of the pipes, one end of each pipe may be formed with a spigot, and the other end of each pipe may be formed with a socket for re ceiving the spigot of an adjacent pipe. The spigots are formed by locating a metal spigot (such as that shown in FIG. 2 at 70) around the mandrel adjacent a plate 60 before threading the longitudinally extending reinforcing wires on the mandrel; subsequent depositing of concrete embeds a part of the spigot in concrete to connect permanently the spigot to the completed pipe. Removable blanking rings are provided around part of the spigot to prevent concrete being deposited on the part of the spigot to project into an adjacent pipe when completed, and, to form the socket at the other end of the pipe, adjacent the other plate 60 at the other end of the mandrel.

A joint between adjacent ends of two completed pipes is shown in FIG. 2, the pipe 72 having a metal spigot 70 attached thereto as described above, and the pipe 73 having a female socket formed therein. A rubber ring 74 completes the joint between the spigot of one pipe and the socket of the other.

In the apparatus described above the tension in the reinforcing wire is created by the difference in peripheral speeds between the pulleys 40 and the mandrel 27. The relative rates of rotation of the pulleys 40 and mandrel 27 are governed by the sprockets 42 and 26. It will be appreciated that it may be desirable to change the relative rates of rotation, and this may be effected by altering the sizes of the sprockets. Alternatively different transmission means may be employed to rotate the pulleys 40 and mandrel 27; for example, variable speed hydraulic motors.

It is convenient to record the tension in the reinforcing wire being wound on to the concrete. This may be effected by deflecting slightly the wire immediately prior to being wound on the green concrete; the force required to deflect the wire is related to the tension in the wire. By continuously recording the tension, a calibration of the tension of the reinforcing wire used in each pipe may be obtained.

We claim:

1. In a method of manufacturing reinforced concrete pipes comprising the known steps of casting a layer of concrete onto the peripheral surface of a mandrel, and winding helically a wire reinforcing member around the concrete layer, the wire reinforcing member being tensioned to form a prestressed reinforcing layer for the concrete pipe; the improvement including the steps of consolidating and retaining the concrete on the mandrel by helically winding a flexible binding member around said layer of concrete before it has set and before the wire reinforcing member is applied, tensioning the wire reinforcing member and winding it under a substantial tension onto the consolidated and retained concrete before it has set, preserving tension in the wire reinforcing member after it is wound onto the concrete and is prevented by the presence of the binding member from cutting into the inner layer of green concrete to any substantial degree, and permitting the concrete to set with the wire under tension and without expansion of the mandrel.

2. A method as claimed in claim 1 wherein the flexible binding member is wound onto the green concrete simultaneously with the flexible reinforcing member, the reinforcing member being wound onto a part of the concrete which has already been wound with the binding member.

3. A method as claimed in claim 1 wherein a further layer of green concrete is deposited on the concrete deposited on the mandrel after binding and reinforcing and before that concrete has set.

4. A method as claimed in claim 1 wherein the flexible binding member used comprises a filamentary or string-like material.

5. A method as claimed in claim 4 wherein the binding member comprises a polypropylene string.

6. A method as claimed in claim 1 wherein the flexible binding member used comprises a tape.

7. A method as claimed in claim 1 wherein two separate reinforcing members are wound simultaneously around the green concrete.

8. A method as claimed in claim 1 wherein the binding member is wound around the concrete as the concrete is being deposited on another location on the mandrel.

9. A method as claimed in claim 1 wherein the mandrel is rotated as the binding member and as the reinforcing members are wound around the deposited concrete.

10. A method as claimed in claim 1 wherein the reinforcing member is tensioned by passing the member around a tensioning pulley before being wound around the green concrete, the pulley being rotated such that its peripheral speed is less than the peripheral speed of the green concrete on the mandrel.

11. A method as claimed in claim 10 wherein the reinforcing member is passed around two pulleys, one arranged for rotation on the end of the cylinder of a hydraulic ram and the other arranged for rotation on the end of the piston rod of the hydraulic ram, there being means to supply fluid at a constant pressure to the ram, the reinforcing member passing around said two pulleys before being wound on the concrete and after passing around said tensioning pulley.

12. A method as claimed in claim 1 wherein longitudinally extending reinforcing members are provided on 8 mandrel is hollow, and is left within the pipe to form a lining therefor.

15. The method of claim 1 wherein the tensioning step is performed by feeding the wire toward the mandrel at a speed which is different from the speed of the periphery of the concrete on the mandrel. 

1. IN A METHOD OF MANUFACTURING REINFORCED CONCRETE PIPES COMPRISING THE KNOWN STEPS OF CASTING A LAYER OF CONCRETE ONTO THE PERIPHERAL SURFACE OF A MANDREL, AND WINDING HELICALLY A WIRE REINFORCING MEMBER AROUND THE CONCRETE LAYER, THE WIRE REINFORCING MEMBER BEING TENSIONED TO FORM A PRESTRESSED REINFORCING LAYER FOR THE CONCRETE PIPE; THE IMPROVEMENT INCLUDING THE STEPS OF CONSOLIDATING AND RETAINING THE CONCRETE ON THE MANDREL BY HELICALLY WINDING A FLEXIBLE BINDING MEMBER AROUND SAID LAYER OF CONCRETE BEFORE IT HAS SET AND BEFORE THE WIRE REINFORCING MEMBER IS APPLIED, TENSIONING THE WIRE REINFORCING MEMBER AND WINDING IT UNDER A SUBSTANTIAL TENSION ONTO THE CONSOLIDATED AND RETAINER CONCRETE BEFORE IT HAS SET, PRESERVING TENSION IN THE WIRE REINFORCING MEMBER AFTER IT IS WOUND ONTO THE CONCRETEE AND IS PREVENTED BY THE PRESENCE OF THE BINDING MEMBER FROM CUTTING INTO THE INNER LAYER OF GREE CONCRETE TO ANY SUBSTANTIAL DEGRE, AND PERMITTING THE CORCRETE TO SET WITH THE WIRE UNDER TENSION AND WITHOUT EXPANNOF THE MANDREL.
 2. A method as claimed in claim 1 wherein the flexible binding member is wound onto the green concrete simultaneously with the flexible reinforcing member, the reinforcing member being wound onto a part of the concrete which has already been wound with the binding member.
 3. A method as claimed in claim 1 wherein a further layer of green concrete is deposited on the concrete deposited on the mandrel after binding and reinforcing and before that concrete has set.
 4. A method as claimed in claim 1 wherein the flexible binding member used comprises a filamentary or string-like material.
 5. A method as claimed in claim 4 wherein the binding member comprises a polypropylene string.
 6. A method as claimed in claim 1 wherein the flexible binding member used comprises a tape.
 7. A method as claimed in claim 1 wherein two separate reinforcing members are wound simultaneously around the green concrete.
 8. A method as claimed in claim 1 wherein the binding member is wound around the concrete as the concrete is being deposited on another location on the mandrel.
 9. A method as claimed in claim 1 wherein the mandrel is rotated as the binding member and as the reinforcing members are wound around the deposited concrete.
 10. A method as claimed in claim 1 wherein the reinforcing member is tensioned by passing the member around a tensioning pulley before being wound around the green concrete, the pulley being rotated such that its peripheral speed is less than the peripheral speed of the green concrete on the mandrel.
 11. A method as claimed in claim 10 wherein the reinforcing member is passed around two pulleys, one arranged for rotation on the end of the cylinder of a hydraulic ram and the other arranged for rotation on the end of the piston rod of the hydraulic ram, there being means to supply fluid at a constant pressure to the ram, the reinforcing member passing around said two pulleys before being wound on the concrete and after passing around said tensioning pulley.
 12. A method as claimed in claim 1 wherein longitudinally extending reinforcing members are provided on and spaced from the mandrel, the longitudinally extending reinforcing members becoming embedded in the concrete as the concrete is deposited on the mandrel.
 13. A method as claimed in claim 1 wherein the mandrel is removed from the pipe when the concrete has set.
 14. A method as claimed in claim 1 wherein the mandrel is hollow, and is left within the pipe to form a lining therefor.
 15. The method of claim 1 wherein the tensioning step is performed by feeding the wire toward the mandrel at a speed which is different from the speed of the periphery of the concrete on the mandrel. 